For both economic and humane considerations there has been growing interest in alternatives to the use of animals in toxicity testing of chemical agents. Tissue culture has the potential to replace animal testing, because, at least in principle, the cultured cells will respond to challenges in ways similar tot he whole organism. For such in vitro approaches to be successful, however, new and sensitive methods to detect cellular activities are required. The long range objective of the SBIR research is to develop an in vitro toxicity assay based on an innovative cell behavior measurement referred to as ECIS (electric cell-substrate impedance sensing). In phase I the feasibility of this approach was demonstrated as experiments correctly ranked several detergents according to their established in vivo toxicity. Phase II studies will extend and refine these measurements and Applied Bio Physics, experts in the ECIS technology, will collaborate with Johns Hopkins School of Hygiene and Public Health, experts in toxicology and alternatives to animal testing. New hardware will be fabricated incorporating ECIS electrodes in a multiwell arrangement, and new software will be written to provide algorithms to collect and analyze data. With this specialized design and the accumulated data from a wide range of toxicants, two beta test sites will be established for final testing and evaluation of this new approach prior to commercialization. PROPOSED COMMERCIAL APPLICATION: Rigorous testing of compounds is now commonplace and a major economic consideration in the development of new drug, cosmetics, etc. If ECIS can be demonstrated to be an effective and sensitive method for in vitro toxicology, it will have considerable commercial potential. It is by nature quantitative and being computer interfaced, requires very little labor to obtain and analyze data making this approach not only precise but very cost effective.